Presently, deformable intraocular lens are being surgically implanted by various techniques. The majority of these surgical procedures in the United States and abroad involve the use of either 1) surgical forceps; or 2) "shooter" devices for mechanically deforming (e.g., folding, compressing, condensing, rolling, etc.) and manipulating the deformable intraocular lens in a manner to allow insertion through a small incision (2.5 to 3.0 mm) in the eye.
STAAR Surgical Company of Monrovia, Calif., the inventors and originators of the deformable intraocular lens with Dr. Mozzocco, have also been the innovators and suppliers of "shooter" devices to the industry. These "shooter" devices have been widely accepted and currently used by surgeons specializing in the implantation of deformable intraocular lenses.
STAAR Surgical Company informally estimates that approximately fifty (50) percent of all surgical procedures involving the implantation of deformable intraocular lens occur with the use of "shooter" devices.
The original "shooter" devices proposed and designed by Dr. Mozzocco were configured to directly receive a loose unprotected deformable intraocular lens. In such devices, the fully exposed deformable intraocular lens could be potentially damaged while loading the "shooter" device with the deformable intraocular lens. In further developing "shooter" type devices, STAAR Surgical Company made the first "shooter" system comprising an injecting device and a separate one-piece foldable lens cartridge having a lens holding portion connected to a nozzle portion. This development resulted in a "shooter" device that became known in the industry as the "STAAR Shooter". The "STAAR Shooter" became available around 1986, and was supplied on an experimental use basis to surgeons participating in clinical studies seeking approval of implantation of deformable intraocular lens in the human eye by the Food and Drug Administration (FDA), which approval occurred in 1991. An example of a prior art shooter device of STAAR Surgical Company is shown in FIGS. 12 and 13.
The prior art shooter device shown in FIGS. 12 and 13 includes a freely slidable plunger that can be advanced by simply pushing on the one end of the plunger. The slidable plunger includes a tip for contacting with the deformable intraocular lens loaded in a foldable type lens cartridge and forcing the deformable intraocular lens through a nozzle portion of the lens cartridge inserted through a small incision in the eye.
The standard method of use of the prior art shooter device comprises the steps of:
1) loading a deformable intraocular lens into an foldable type lens cartridge opened for receiving the deformable intraocular lens in a flat configuration;
2) closing the foldable type lens cartridge which causes the deformable intraocular lens to fold inside the passageway through the lens cartridge;
3) inserting the loaded lens cartridge into the "STAAR Shooter" device;
4) inserting the tip of the nozzle portion of the lens cartridge through the incision into the eye;
5) advancing the plunger by pushing on the end of the plunger with the thumb while gripping the finger grip connected to the barrel with index finger above and middle finger below so that the tip of the plunger enters into the end of the passageway through the lens cartridge, and then contacts with a trailing end of the deformable intraocular lens; and
6) further advancing the plunger by further pushing on the end of the plunger so that the plunger tip forces the deformable intraocular lens through the passageway in the lens cartridge and out through a tip of the nozzle portion extending through the incision in the eye, thus, allowing the unconstrained deformable intraocular lens to open up (i.e. unfold or decompress) inside the eye.
The manner in which the deformable intraocular lens is released from the tip of the nozzle portion inside the eye can be an important factor with respect to the degree of success of the surgical procedure, and risk of harm or damage to eye tissue during the surgical procedure. In order to increase the degree of success of the surgical procedure and minimize the risk to the patient, it is highly desirable that the deformable intraocular lens is released in a controlled manner, since uncontrolled release of the deformable intraocular lens could cause eye damage. Specifically, due to the resilient nature of the plastic material of the deformable intraocular lens and the plastic material of the nozzle portion of the lens cartridge, the deformable intraocular lens has a tendency to shoot out of the end of the tip of the nozzle portion when uncontrollably released. This phenomenon occurs due to the highly compressed or constrained (i.e. "stressed") configuration of the deformed intraocular lens attempting to expand inside the nozzle portion having resilient walls. When a certain portion of the deformable intraocular lens is extruded or projected a certain critical distance outside the opening of the tip of the nozzle portion, the "stressed" lens will tend to suddenly release and shoot out of the tip of the nozzle portion into the interior of the eye. This phenomenon can result in torn capsular bags and/or damage to tissue in the anterior and posterior chambers in some cases.
In order to control the release of the intraocular lens, various known modifications to the shooters and lens cartridges have been made, and insertion techniques have also been modified. For example, the tip of the nozzle portion can be provided with slits that control the opening and alleviate the expansion force of the folded or compressed intraocular lens exiting the tip of the nozzle portion. Further, the plunger in some shooters is not freely slidable, but instead provided with threaded means for advancing the movement of the plunger. For example, STAAR Surgical Company currently provides a "shooter" under the Model No. MSI-T having a plunger with threaded advancement means allowing for highly controlled fine advancement of the plunger, which provides some controlled release of the deformable intraocular lens.
However, this type of "shooter" having threaded advancing means for controlling the movement of the plunger is not considered desirable by some high volume and high skilled surgeons performing multiple surgical procedures one after another, since any means for restricting the movement of the plunger impedes the surgeon increasing the time for each procedure and potentially limits the maneuverability of the "shooter".
Thus, it is highly desirable to improve both the devices and methods of implanting the deformable intraocular lens in the eye to provide controlled released of the deformable intraocular lens into the eye, and for decreasing the time of the surgical procedure. Also, the ergonomic "feel" for the surgeon using the "shooter" devices can be enhanced by "shooters" according to the present invention tending to increase surgical efficiency and decrease the risk to the patient.